It is known that an expanded molded article formed from a polystyrene-based resin has superior rigidity, thermal insulation properties, lightweight properties, water resistance, and expansion moldability. For this reason, this expanded molded article is used widely as a cushioning material and as a thermal insulating material for building materials. However, an expanded molded article formed from a polystyrene-based resin had the problem that chemical resistance and impact resistance are inferior.
On the other hand, it is known that an expanded molded article formed from a polyethylene-based resin has superior chemical resistance and impact resistance. For this reason, this expanded molded article is used in vehicle-related components. However, since retention of the blowing agent is inferior for a polyethylene-based resin, it is necessary to closely control the expansion molding conditions. For this reason, there was the problem that production costs are high. In addition, there was also the problem that the rigidity of this expanded molded article is inferior compared to an expanded molded article formed from a polystyrene-based resin.
In order to solve the above-mentioned problems of expanded molded articles formed from a polystyrene-based resin or a polyethylene-based resin, an expanded molded article obtained from composite resin particles of a polystyrene-based resin and a polyethylene-based resin has been reported. This expanded molded article has both the superior rigidity and expansion moldability of a polystyrene-based resin and the superior chemical resistance and impact resistance of a polyethylene -based resin. Furthermore, in Japanese Patent No. 4072553 (Patent Document 1) and Japanese Patent No. 4072554(Patent Document 2), it is reported that composite resin particles including a linear low-density polyethylene-based resin give an expanded molded article having further improved impact resistance. Also, in Japanese Unexamined Patent Application, First Publication No. 2007-270116 (Patent Document 3) and Japanese Unexamined Patent Application, First Publication No. 2010-24353 (Patent Document 4), it is reported that composite resin particles including a high-density polyethylene-based resin having specific physical properties give an expanded molded article for which the temperature dependency of mechanical properties is suppressed.